Genome-wide identification and analysis of elongase of very long chain fatty acid genes in the silkworm, Bombyx mori

Very long chain fatty acids (VLCFAs), such as sphingolipids, are components of cellular lipids, which are essential for cell proliferation. Mutations in the genes that encode proteins participating in VLCFA biosynthesis may cause inherited diseases, such as macular degeneration. Elongases of very long chain fatty acid (ELOVL) are enzymes that are involved in the biosynthesis of VLCFAs. Here, a total of 13 ELOVL genes, distributed across three chromosomes, were identified in the silkworm genome; all the ELOVL members contain a distinct ELO domain and a conserved HXXHH motif. Phylogenetic reconstruction was performed to analyze the evolutionary relationships among different species and to predict gene functions. The 13 ELOVL genes were assigned to the ELOVL3/6, ELOVL1/7, and ELOVL4 clades. Microarray and semiquantitative PCR analyses indicated that these genes are differentially expressed among various tissues, in turn suggesting functional divergence in the growth and development of each tissue. Further investigation showed that the expression level of the BGIBMGA000424 gene is significantly negatively correlated with the cocoon-shell weight among different silkworm strains. Taken together, the present study is the first comprehensive analysis of ELOVL genes in silkworm, and the results may serve as a foundation for further analysis of the physiological functions of ELOVL genes in silkworm.